#include<bits/stdc++.h>
using namespace std;

class Solution {
public:
    int maxProfit(vector<int>& prices) {
        int n = prices.size();
        int dp[n][2];
        memset(dp,0,sizeof dp);
        dp[0][0] = 0;
        dp[0][1] = -prices[0];
        for(int i=1;i<n;i++){
            dp[i][0] = max( dp[i-1][0], dp[i-1][1]+prices[i] );
            dp[i][1] = max( dp[i-1][1], -prices[i] );
        }
        return dp[n-1][0];
    }
};